Fan control circuit

ABSTRACT

A fan control circuit of a computer includes a fan interface connected to a connector of a fan, a fan controller, a NOT gate, and an electronic switch. The fan controller outputs a PWM signal to the fan interface to control the operation of the fan, and includes a GPIO interface to output a voltage control signal to the NOT gate to switch the electronic switch on or off. A signal output of the electronic switch is connected to the fan interface. The voltage control signal is high level at the start up moment of the computer, and thus does not turn on the fan via the electronic switch. After a preset delay period, the voltage control signal is turned low by the fan controller so that the fan interface receives the PWM signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to a U.S. patent application entitled “FAN CONTROL CIRCUIT,” with the same assignee as the instant application and with application Ser. No. 13/228,462. The disclosure of the above identified application is incorporated herein by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a fan control circuit.

2. Description of Related Art

A server typically includes multiple fans, which rotate at full speed at the moment of the server being started up. The power consumed by the interior components of the server, such as motherboards, hard disk drives and fans, can be up to a thousand kilowatts at the start up moment, which may cause instability in the power supply to the server, and high power consumption. Delay circuitry has been used to make the fans start operating after a preset delay period, however, many delay circuits include multiple extra components, which results in high cost.

BRIEF DESCRIPTION OF THE DRAWING

Many aspects of the embodiments can be better understood with reference to the following drawing. The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments.

The drawing is a block diagram of an exemplary embodiment of a fan control circuit connected to a fan via a fan connector.

DETAILED DESCRIPTION

The disclosure, including the accompanying drawing, is illustrated by way of example and not by way of limitation. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.

Referring to the FIGURE, an exemplary embodiment of a fan control circuit 100 of a computer includes a fan controller 90, an electronic switch chip 40, a NOT gate 50, and a fan interface 30 for connecting with a connector 25 of a fan 20.

The fan controller 90 includes a rotational speed control pin 16 which outputs a pulse width modulation (PWM) signal, and a general purpose input/output (GPIO) interface 95 with a control pin 12 for outputting a voltage control signal. The rotational speed control pin 16 is connected to a control pin 14 of the fan interface 30 to transmit the PWM signal to the fan interface 30 to control the operation of the fan 20. The control pin 12 of the GPIO interface 95 is connected to the input of the NOT gate 50 for outputting the voltage control signal, which is at a high level at the moment of the computer being started up, and after a delay period, becomes a low level signal under the control of the fan controller 90.

The electronic switch chip 40 (e.g. NC7SV125P5X_DS chip) includes an enable terminal OE, a signal input A, and a signal output Y. The enable terminal OE and the signal input A of the electronic switch chip 40 are connected to the output of the NOT gate 50, and the signal output Y is coupled to the rotational speed control pin 16 of the fan controller 90. The electronic switch chip 40 is turned on when the enable terminal OE of the electronic switch chip 40 receives a low-level voltage control signal.

As the computer starts up, the control pin 12 of the GPIO interface 95 outputs a high-level voltage control signal to the input of the NOT gate 50. The NOT gate 50 inverts the signal which is then output to the enable pin OE and the signal input A of the electronic switch chip 40. The electronic switch chip 40 is turned on, and the low-level signal from the signal input A of the electronic switch 40 is transmitted to the rotational speed control pin 16 of the fan controller 90 via the signal output Y of the electronic switch chip 40. The governing signal at the rotational speed control pin 16 and the control pin 14 of the fan interface 30 is thereby low, which leaves the fan 20 turned off.

After a preset delay period, the voltage control signal at the control pin 12 of the GPIO interface 95 becomes a low-level signal under the control of the fan controller 90. The NOT gate 50 inverts again, and the resulting high-level signal is then sent to the enable terminal OE to turn off the electronic switch chip 40. The control pin 14 of the fan interface 30 receives a PWM signal from the rotational speed control pin 16 of the fan controller 90 to start and control the operation of the fan 40.

The foregoing description of the exemplary embodiments of the disclosure has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible. The embodiments are described in order to explain the principles of the disclosure and their practical application so as to enable others of ordinary skill in the art to utilize the disclosure, with such various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those of ordinary skills in the art to which the present disclosure pertains without departing from its spirit and scope. Accordingly, the scope of the present disclosure is defined by the appended claims rather than by the foregoing description and the exemplary embodiments described therein. 

What is claimed is:
 1. A fan control circuit of a computer, the fan control circuit comprising: a fan interface connected to a connector of a fan of the computer, and comprising a first control pin; an electronic switch comprising an enable terminal, a signal input and a signal output, wherein the electronic switch is turned on when the enable terminal receives a low-level signal; a NOT gate comprising an input and an output, the output connected to the enable terminal and the signal input of the electronic switch; and a fan controller comprising a general purpose input/output (GPIO) interface and a rotational speed control pin, the rotational speed control pin connected to the signal output of the electronic switch and the first control pin of the fan interface, the GPIO interface comprising a second control pin connected to the input of the NOT gate for outputting a voltage control signal, wherein the voltage control signal is at high level at the moment of the computer being started up, and the output of the NOT gate outputs a low-level signal to the enable terminal of the electronic switch, the electronic switch is turned on, and transmits the low-level signal to the first control pin of the fan interface, thereby the fan is not turned on; after a preset delay period of time after the computer is started up, the voltage control signal at the second control pin of the GPIO interface becomes a low-level signal under the control of the fan controller, and the NOT gate outputs a high-level signal to turn off the electronic switch, the rotational speed control pin of the fan controller outputs a pulse width modulation (PWM) signal to the first control pin of the fan interface to control the operation of the fan. 